Method of producing unsaturated hydrocarbons



Patented Dec. 22, 1936 PATENT OFFICE METHOD or raonucmo unsaronarnn nrnaoomons Charles A. Thomas, Wayne, and John F. Olin,

Newtown Square, Pa., assignors to The Sharples Solvents Corporation, Philadelphia, Pa.,, a corporation oi Delaware No Drawing. Application June 15, 1933, Serial No. 675,968

2Claims.

The present invention relates to the production of unsaturated hydrocarbons and is particularly concerned with the production of hydrocarbon material containing a relatively high 5 proportion of olefins having from 12 to 30 carbon atoms. The principal object of the invention has been to produce a mixture of this type which is substantially free of dioleflns and other compounds of a higher degree of unsaturation than the olefin material'desired. A further ob- V ject has 'been to produce a mixture of this type which contains only a relatively small proportion of saturated hydrocarbons or impurities.

In the preferred practice of the invention, a

15 petroleum hydrocarbon fraction of desired boiling range containing alarge proportion of saturated hydrocarbon of the paraffinseries is first chlorinatedand the chlorinated hydrocarbon is thereafter subjected to a splitting operation to decompose the chloride molecules by the splitting of hydrogen chloride from these molecules to produce the desired olefin.

. A feature of the invention consists in the utilization of proportions of reactants adapted to 5 eliminate difliculties of fractionation .which might otherwise arise in attempts to obtain a mixture of olefin material containing but a small proportion of saturated hydrocarbons.

A second feature of the invention consists in the practice of a method of splitting the chlorinated hydrocarbon which largely avoids the formation of diolefins and likewise avoids the ex; cessive re-combination of the hydrogen chloride split from the chlorinated material with olefin to re-form the alkyl chloride molecules. Further features relating to the economical performance of the process to obtain a high yield of the desired product will be obvious from a reading of the following description of the process.

In the practice of the invention, a hydrocarbon mixture consisting principally of saturated hydrocarbon material is first obtained by careful distillation of hydrocarbon material obtained from petroleum. This hydrocarbon material is subjected to a chlorinating operation by passing chlorine in vapor phase into the mixture while maintaining the temperature of the mixture substantially low, preferably below 100 C. The passage of chlorine into'the hydrocaro bon mixture, is continued until the gain in weight of the hydrocarbon material indicates that the chlorinationreaction has proceeded to the substantial completion of the chlorination of the entire hydrocarbon mixture. To this end, it u is preferred .to continue the chlorination until completion.

a quantity of chlorine which is in substantial molecular excess of the quantity of hydrocarbon under treatment has reacted therewith. A ratio of 1.5 moles of chlorine per mole of hydrocarbon i has been found to eflect a satisfactory chlorination of the hydrocarbon.

When the increase in the weight of the hydrocarbon material indicates that the chlorination reaction has been substantially completed, the to entire body of chlorinated hydrocarbon is subjected to a catalytic splitting reaction to cause the separation of hydrogen chloride from the alkyl chloride molecules.

An important feature of the invention con- 1 sists in the performance of this reaction upon the entire body of chlorinated material in the liquid phase without the performance of any fractionation of the chlorinated material prior to the splitting reaction. The chlorinated hydrocarbon is refluxed in contact with a suitable 20 catalyst chosen from the classes of metallic chlorides and oxides, this splitting operation being performed in such a manner as to avoid any passage of hydrocarbon material overhead during this stage of the operation. The hydrogen 26 chloride split from the alkyl chloride molecules is passed overhead during the refluxing of the mixture of hydrocarbon and alkyl chloride, thus removing the hydrogen chloride evolved as the result of the splitting operation from the zone 30 of reaction. The refluxing operation is preferably continued for several hours and yields a material containing a very high proportion of unsaturated hydrocarbon.

The residue is next distilled and the overhead 35 material collected. It yields a fraction of approximately the same boiling range as the hydrocarbon originally chlorinated, this fraction containing a large proportion of the desired olefin. The residue of this distillation includes alkyl chlorides, chlorolefins, unchanged hydrocarbon and catalyst.

The advantages of the practice of the invention should be obvious from the above description. By the utilization of a quantity of chlorine in substantial molecular excess of the amount of hydrocarbon material treated, the chlorination of this material proceeds to substantial 4 This fact has a very important bearing. on the eflicient practice of the process, for olefin material of the range desired is very diflicult to separate from corresponding paraflin hydrocarbon, these compounds of similar carbon content having approximately the s e boiling range. It is. therefore, highly impdrtant that the olefin material of the mixture be contaminated with as little paraflin as possible, in order that a mixture containing a large preponderance of olefin may be obtained without recourse to elaborate fractionation of the ultimate material produced by the process.

Further important advantages are obtained by the liquid phase splitting of the chlorinated molecules in the manner described above. W The performance of the splitting operation in the liquid phase renders possible an operation in which the material under treatment is gradually refluxed and hydrogen chloride separated by the splitting operation is removed as it is formed. This fact has an important bearing upon the emcient performance of the process, as it not only avoids contamination with hydrogen chloride of the mixture ultimately -obtained, but it avoids re-combination of this hydrogen chloride with the unsaturated hydrocarbon to re-form the alkyl chloride molecules. It will be appreciated that re-formation of these alkyl chloride molecules out of contact with the splitting catalyst would defeat the very purpose of the splitting operation. In the practice of the process as described, any re-combination which may occur takes place in the presence of the splitting catalyst and the re-chlorinated product is thus subjected to the same splitting action which causes the original splitting of the molecule.

Performance of the splitting operation in the liquid phase and the refluxing of the hydrocarbon material also avoid the accidental passage of hydrocarbon chloride from the zone of reaction and enable us to gradually complete the split- I ting operation to the desired degree without the necessity of recycling any of this material.

. The importance of the particular nature of the splittingoperation will also be apparent from the following theoretical considerations. When a saturated hydrocarbon is chlorinated, a mixture of chlorides and polychlorides is formed. These polychlorides are formed in part by reason of the attack of chlorine upon more than one of the hydrogen atoms of the hydrocarbon molecules under treatment and in part by the splitting of hydrocarbon chlorides formed and the attack of chlorine molecules upon the double bonds of olefins formed by the splitting reaction. When a dichloride is split to remove both of its chlorine molecules, a diolefin is produced. Since these diolefins and olefins of higher degrees of unsaturation constitute undesired constituents of the mixture, their avoidance constitutes an important advantage of the procedure adopted. When a dichloride is subjected to a splitting reaction, it is first decomposed to form the corresponding chlor-olefin. When the chlorolefin is subjected to more intense splitting conditions, it may be split to form the corresponding diolefin. The splitting of chlor-olefins of a given carbon content to form diolefins requires much more intense reaction conditionsfrom the standpoint of heat and catalysts, however, than doesv the splitting of corresponding alkyl chlorides. By the performance of the splitting reaction in the liquid phase under reflux conditions and in the presence of suitable catalysts, in the practice of the present invention, we have succeeded in selectively splitting the alkyl chloride molecules to the substantial exclusion of the chlor-olefin of the mixture. I

Thus, where a paraffin of the formula CnH2n+2 is chlorinated, we get a mixture including alkyl monochlorides and alkylene dichlorides of the following type formulae:

( c,.n,..+,ci

An alkyl chloride n in i An alkylono dichloride When a mixture including compounds of the types indicated at I and II is subjected to splitting conditions, compound I decomposes to form an olefin of the type formula CnHZn. Under these conditions, compounds of the type indicated at II are first decomposed to split off a molecule of hydrogen chloride and form chlorolefins of the type formula CnHfl'n-ICI. If these chlor-olefins are subjected to intense splitting conditions, they may lose an additional molecule of hydrogen chloride to form diolefins of the type formula CblHzn-z.

It is the object of the invention to produce a mixture containing a large preponderance of olefins to the substantial exclusion of chloroleflns, diolefins, and more highly unsaturated hydrocarbons or their chlor-derivatives. If a splitting operation of such intensity is adopted as to cause the production of a substantial quantity of diolefin material, a difllcult problem of fractionationis presented in connection with any attempt to separate this diolefin material from the desired olefin. By the careful practice of liquid phase splitting in the presence of a suitable catalyst and under reflux conditions, the splitting of the chlor-olefin material to form the undesired diolefin is substantially eliminated. Since the alkyl chlorides can be more readily split than the corresponding chlor-olefins, it is possible to choose reaction conditions in the splitting operation adapted to effect the selective splitting of the alkyl chlorides to the substantial exclusion of the chlor-olefins and more highly unsaturated chlor-compounds. At the conclusion of the reaction, it is possible to separate the olefins formed, together with the other unchlorinated hydrocarbon material of the mixture and retain the chlorinated material including alkyl chlorides, alkylene dichlorides, higher chlorides and unsaturated chlor-compounds in the residue.

A number of catalysts chosen from the classes of metal salts have been found to be satisfactory in the performance of the splitting reaction in the practice of the invention. Thus, the metal chlorides such as ferric chloride, ferrous chloride, ouprous chloride, cupric chloride, cobalt chloride, cadmium chloride, antimony chloride, zinc chloride, barium chloride and manganese chloride have been found satisfactory in this connection. Iron oxide and mixtures thereof with one of the chlorides referred to above have also been found to have the desired catalytic eifect. It is necessary to use only a very small amount of catalyst, one-half of one per cent of ferric chloride having been found to be'satisfactory in the splitting of tetra-decyl chloride.

As an illustrative example of the practice of the invention, the following procedure was adopted. 200 pounds of hydrocarbon material obtained by the careful fractionation of Cabin Creek kerosene, and having an Engler distillation range from 243 to 258 degrees C. and having a specific gravity of 0.795 was chlorinated by the passage of chlorine through the hydrocarbon material until the chlorinated material had a weight of 252.5 pounds. This increase in weight represents a molecular ratio of chlorine to hydrocarbon of 1.5:1. By continuing the chlorination reaction until the weight of the material under treatment indicates the presence of a substantial molecular excess of chlorine, the operator can assure himself that the major proportion of the hydrocarbon material has been chlorinated. The specific gravity of the chlorinated material at 20 degrees C. was approximately 0.954. At

, the completion of the chlorination reaction, 1.2

. sequent stages oi the operation. After the evolution of hydrogen chloride had entirely ceased, the hydrocarbon material remaining in the still was distilled under reduced pressure to obtain a mixture containing a preponderance. of olefin. The fraction having a boiling range from 155 to 175 C. at 100 mm. pressure was collected and contained from 80 to 85 percent of olefin having a specific gravity of 0.810. 110 pounds of olefin containing material were obtained. The olefin material contained a small amount of hydrogen chloride which was neutralized by washing with a one percent sodium hydroxide solution and decanting the mixture so obtained to effect the removal of brine.

When the term a narrow boiling hydrocarbon fraction is used in the subjoined claims, this term is used to designate a hydrocarbon fraction of such narrow boiling range that the chlorides and chlor-olefins corresponding in carbon content to the lowest boiling hydrocarbon constituents of the fraction have higher boiling points than the highest boiling oleflns corresponding in carbon content to the highest boiling hydrocarbon constituents of said fraction.

Modifications will be obvious to those skilled in the art. The practice of chlorinating a hydrocarbon mixture of the type under treatment with an excess of chlorine to insure the formation of a mixture of monoand poly-chlorides with a minimum of hydrocarbon may, for example, be practiced in connection with other subsequent steps of splitting of the chlorides "than those discussed above. Similarly, the particular method of liquid phase splitting adopted may be used in connection with other methods of halogenation than that described. Still other modifications may be adopted and we do not, therefore, wish to be limited except by the broad scope of the subjoined claims.

We claim:

1. The method of producing unsaturated ali phatic hydrocarbon material containing twelve or more carbon atoms and separating said unsaturated aliphatic hydrocarbon material from by-products produced in the manufacture thereof which comprises chlorinating to substantial molecular excess paraffine hydrocarbon material of a carbon content corresponding to the desired unsaturated hydrocarbon and consisting of a narrow boiling hydrocarbon fraction, splitting hydrogen chloride from the chlorinated material in the liquid phase to produce the desired unsaturated hydrocarbon, and thereafter separating the desired unsaturated hydrocarbon from the mixture resulting from the splitting operation by distilling said unsaturated hydrocarbon overhead from undesired chlorine derivatives obtained as byproducts.

2. The method of producing unsaturated aliphatic hydrocarbon material containing twelve or more carbon atoms and separating said unsaturated aliphatic hydrocarbon material from by products produced in the manufacture thereof which comprises chlorinating by substitution parafilne hydrocarbon material of a carbon content corresponding to the desired unsaturated hydrocarbon and consisting of a narrow boiling hydro- 'carbon fraction, the chlorination of the hydrocarbon being continued until the reaction of a substantial molecular excess of chlorine with the hydrocarbon to produce a mixture of mono-chlorinated and poly-chlorinated derivatives of said parafline hydrocarbon containing not more than a relatively small proportion of unchlorinated hydrocarbon is completed, subjecting said mixture to a liquid phase splitting reaction of controlled degree adapted to effect the splitting of hydrogen chloride from the mono-chlor derivatives of saturated hydrocarbons and thereafter separating desired unsaturated hydrocarbon material so formed from the undesired chlorine derivatives obtained as by-products by distilling said unsaturated hydrocarbon material overhead from undesired material.

CHARLES A. THOMAS.

JOHN F. OLIN. 

